Environmental noise pollution chapter 8 – conclusions and future directions

C H A P T E R

8

Conclusions and Future
Directions
Environmental noise pollution is a complex issue. The previous chapters
in this book illustrate the multifarious nature of issues surrounding the
understanding and control of sound that is out of place. The problem with
noise pollution though is that it is not only a complex issue but also a highly
persistent one. As a public nuisance concern, it has been steeped in the
awareness of the public consciousness for millennia but has not really been
taken seriously enough by policymakers who have tended to prioritise
other seemingly more pressing environmental issues. And so, despite
centuries of scientific endeavour along with attempts to control and mitigate noise, the problem continues to rumble on. Indeed, the rise in the ownership and use of private transport over the last century has arguably
turned the rumble of noise pollution into something of a roar.
Until relatively recently, there was certainly some truth in the notion of
environmental noise as the forgotten pollutant. Others (such as air pollution and stench) have been given much greater attention in policymaking
over the last century and, while they have not been eliminated entirely,
they have certainly been controlled to a much more significant degree.
In fact, one might be forgiven for thinking that the damage (in terms of
public health and general annoyance) associated with noise pollution is
not really improving at all. Certainly, of all pollutants, noise is one that
is practically impossible to escape from in our daily lives. The rapid urbanisation of populations witnessed throughout the globe over the last century combined with the growth in private transport has meant that
both neighbourhood noise annoyance and noise from transportation
sources are becoming a more pressing problem.
However, these are not the only reasons why noise is still a major
contemporary pollution issue. There are numerous reasons. A crucial
additional one is alluded to by Goldsmith (2012) who informs us that
because the ear evolved largely as a warning system, noise is considered

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Copyright # 2014 Elsevier Inc. All rights reserved.


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by humans to be intrinsically disturbing. This relationship is what gives
the ear its extraordinary sensitivity allowing it to detect even the slightest
flows of wave energy in the air. As Goldsmith (2013, p. 269) points out:
‘even a perfectly sound-proofed building is hardly better than a shoddy
one if the smallest of its windows is broken’. Indeed, this is also what
makes mitigating noise pollution such a difficulty – it is very much an
all-or-nothing kind of business. In other words, partially mitigating noise
will have very little effect on the level of disturbance being felt by a person
subjected to noise. Moreover, precisely because some people are more sensitive to noise than others, it means that reducing noise below a certain
level may be acceptable to one person but not to another who might still
feel disturbed.
The issue of the subjective nature of noise annoyance poses quite a
problem for those who are interested in developing and standardising
units of measurement that convey the extent of the intensity of noise.
We know that the decibel and the A-weighted system were developed
precisely for this purpose, but they are far from being perfect. We also
know that the various indicators used to measure annoyance and disturbance are fairly crude in that they do not adequately deal with the varying
range of subjective human responses to different noise sources, nor do
they deal adequately with different types of noise, in particular impulsive,

intermittent and low-frequency noise. And of course, all of these issues
pose problems for policymakers that are attempting to regulate the extent
of noise.
It is also important that we do not forget the major societal changes that
have occurred over the last half century which has made the problem of
noise pollution even more difficult and complex to tackle. The traditional
past societal arrangement of individuals working a typical 9–5 day has
changed significantly with increasingly flexible working arrangements
bringing about a more varied ‘working day’ which can often overlap with
the night-time period. Of course, greater night-time activity means that
that noise is becoming increasingly difficult to control during traditional
sleeping hours between 11 pm and 7 am and this is where the major problem lies in terms of the health implications of noise-induced sleep disturbance and related secondary effects. Other changes in the way city regions
are planned and organised over the last half decade have also impacted on
noise pollution. The traditional past approach of mono-functional zoning
where polluting activities (e.g. heavy industry, manufacturing) were
separated from residential areas is no longer typical practice in urban
and regional planning. The restructuring of western economies away
from manufacturing industry to more service-oriented and ‘cleaner’
industry has allowed for more mixed-use zoning systems to be adopted.
In fact, this approach is now considered best international practice in the
vast majority of developed countries. Thus, employment, housing, retail


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and entertainment facilities now exist adjacent to each other in urban
areas, meaning that the noise produced from the intermixing of these land
use activities (e.g. commuting, socialising, shopping among others) is felt

to a much larger degree by present-day households than by households
under past land use arrangements.
While the tone of the foregoing discussion might suggest then that the
problem of environmental noise is getting worse, it is merely attempting to
reflect more broadly on the situation in which we find ourselves. There
really is no concrete way to determine if noise pollution is better or worse
now than it was a century ago because the socio-political context was very
different then than what we have today. Moreover, how noise was understood, measured and controlled was also very different than current practices while modern technologies simply cannot be compared to those
existing even in the relatively recent past. Broadly then, it is virtually
impossible to compare the noise situation today with centuries ago
because there is simply no common basis for such a comparison. Nor
are we suggesting that noise is an insoluble problem or, more importantly,
that no progress has been made in understanding environmental noise, its
human impacts and how we might control it. On the contrary, progress
has been very significant indeed. Many of the major noise sources discussed in this book – automobiles, trains, airplanes – are now subject to
much stricter noise limits than they were at any point in the past. Noise
from industrial equipment (and therefore industry more generally) is similarly subject to much stricter limits. In addition, many nations have legislated for night-time noise limits at the point of the receiver, modern
homes tend to be built with better sound proofing, and mitigation measures have become more effective. And yet, the inescapable (and somewhat depressing) conclusion of the World Health Organisation (WHO)
is that ‘the trend [for] noise exposure is increasing in Europe compared
to other stressors (e.g. exposure to second hand smoke, dioxins and benzene), which are declining’ (WHO, 2011, p. 1).
On the face of it, all of this comes across as something of a contradiction –
how can we be making progress while the problem is getting worse?
The answer of course is that while progress is indeed being made, it is
being achieved within the context of a massive increase in the volume of
noise-related activity – populations are growing, population distribution
is becoming increasingly concentrated and private vehicle ownership
and use are increasing at the same time as the role of public transport is
declining and these issues have placed significant limits on the impact of
progress that has been made. In the context of this book, this is quite a crucial point. The reason is that, quite aside from the book’s important description of the technical detail associated with noise pollution, the general
narrative running through this chapter has focussed on conveying two

key issues. The first is that it documents the progress that has been made over


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the recent past in understanding the nature of environmental noise pollution, its effect on humans and how it can be better understood and assessed
to ensure more effective mitigation and control. The second issue relates to
the book’s implicit focus on the limitations of existing knowledge/understanding in the aforementioned areas of environmental noise pollution
and how they might be improved in terms of both future research and
practice.

8.1 PROGRESS
Perhaps the most important reason that has contributed to driving progress in our knowledge of environmental noise over the last half century
relates to our understanding of the relationship between noise and human
health. In particular, we now know much more about the relationship
between doses of environmental noise and their direct and indirect health
effects as outlined in Chapter 2. There is little doubt that our enhanced
knowledge of the detrimental health impacts of long-term noise exposure,
even at relatively low levels, has been the catalyst for environmental noise
issues to become an important environmental and public health policy
consideration.
In relative terms, there has been an explosion of research on the health
effects of environmental noise over the last half decade. We have moved
from a situation where the nature of dose–effect relationships was only
partially understood to a situation where scholars now have a relatively
good handle on the nature of the public health problem caused by exposure of populations to excessive environmental noise. As elucidated in
Chapter 2, we now know that excessive exposure either causes or is
directly associated with a range of health effects, not only primary effects

such as sleep disturbance but also a range of secondary effects that are felt
as a result of disturbed sleep. We know that the primary effects of noise
exposure on health are in terms of annoyance, sleep disturbance, cardiovascular disease, tinnitus and cognitive impairment in children. For example, it is only in the last 20 years that a clear association has been
established between noise exposure and higher incidence of cardiovascular disease which has been a major leap forward in understanding.
Research has also taught us that annoyance and sleep disturbance resulting from noise pollution exposure act as a significant health stressor which
can lead to and/or trigger more serious health problems.
Moreover, the emergence of the DALY1 has only recently allowed for a
quantification of the health effects of environmental noise at the EU level
1

Daly is a disability-adjusted life year. See Chapter 3 (Box 3.1) for a broader explanation
of its origin and Section 3.1 for technical details.


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(see Table 3.1) which was not possible a half decade ago. Our understanding of not only the nature of the dose–effect health relationships but also
the scale of the problem across the globe is considerably improved.
Indeed, the scale of the problem is quite staggering and yet we still do
not quite have a complete grasp of it. In 1999, the WHO estimated that
almost 50% of European citizens lived in grey areas of acoustical discomfort. While the composition of the EU has changed considerably in the
intervening period, the first phase of noise mapping (conducted in
2007) showed that approximately 40 million people across the EU are
exposed to noise above 50 dB(A) from roads within agglomerations during the night with a further 22 million exposed outside agglomerations.
Given that the WHO (2009) sets 40 dB(A) night-time as the value above
which health effects are noticeable (see Chapter 3), these figures emphasise quite clearly not only the (almost) ubiquitous nature of the problem
but the fact that the potential problems associated with the overexposure
to noise pollution are at such a scale as to consider it a major public health

issue for policy makers. But of course, the health effects are not confined to
the EU – it simply happens to be the one continent for which we have
decent data on the scale of noise pollution exposure. What the European
case shows is that environmental noise is a global problem and no nation is
immune from its associated problems.
As a direct consequence of improvements in our understanding of the
noise–health relationship, noise policy and legislation have underwent
very significant and positive changes throughout the EU. As it now
stands, there is little doubt that the EU has the world’s most progressive
noise legislation and policy in terms of attempting to protect its citizens
from the detrimental effects of excessive exposure to environmental noise
pollution. Quite important is the fact that many other nations beyond the
EU have looked towards what the continent has been doing and, while
few nations have taken identical steps, there would certainly appear to
be much more cognisance of noise as an environmental and public health
problem in other nations as a result of EU legislative and policy changes.
Since the 1970s, the EU has consistently legislated for stricter permissible
noise limits on manufacturers of automobiles, trains, aircraft, outdoor
equipment, recreational craft and household appliances. Table 4.1
(Chapter 4) provides a good illustration of the range of legislative Directives that have been issued in these areas. Utilising legislation to drive
down permissible noise limits has forced manufacturers to improve their
technologies in such a way that they now make much quieter vehicles and
appliances than they did in the past.
There is little doubt also that the introduction of the Environmental
Noise Directive (END) into legislation in 2002 has been important in
getting to grips with the extent of the noise problem across the EU
but it has, perhaps, been even more important in raising awareness of


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environmental noise as a major environmental concern as well as a public health problem. For the first time, the END has provided a strategic
approach to assessing and controlling the environmental noise problem
at a supra-national level and this has been a major progression. While
the END still only provides estimates of the population exposed across
the EU, it has provided the first real glimpse of the scale of exposure
across the Union. And as mentioned already, the scale of the problem
is considerable. Moreover, these estimates were used as the basis for
quantifying the extent of the disease burden associated with night-time
noise exposure across the EU in the WHO’s recent Burden of Disease from
Environmental Noise document. This would not have been possible without estimates of population exposure arising from the END. Moreover,
the END has also provided a strategic framework for nations within
the EU to work together, share information and best practice approaches
towards understanding how best to assess and control noise as a pollutant. More broadly, it has facilitated enhanced co-operation among
responsible authorities right across the EU and indeed within individual
EU nations. All of this represents significant progress. Prior to its introduction, some nations did indeed take the problem of environmental
noise seriously, but for others, it was barely on the policy radar. Effectively, because the END mandates a strategic approach across the continent, it has meant that all nations are at least ensuring minimum
compliance and engagement with the problem of environmental noise
pollution and this is a considerable step in the right direction even if
there remains significant work to be done. Indeed, it is quite clear that
it is only through a strategic approach that progress can be made on
reducing the harmful effects of noise pollution for citizens.
On the technical side, there has also been considerable progress in noise
prediction capabilities although perhaps not as much as one might like.
Nevertheless, there are a number of significant achievements to note. Perhaps the most noteworthy relates to the ongoing development of common
noise calculation models for road, rail, air and industry across the EU.
It has long been argued that unless noise calculation is standardised across
the EU, it is very difficult to compare the results of population exposure

estimates (Murphy and King, 2010). At the EU level, research funding has
been provided to support movements in this direction since the turn of
the century beginning with the HARMONOISE project and culminating
in the standardised CNOSSOS-EU noise calculation model which is due
to be introduced and utilised by all nations in the 2017 round of strategic
noise mapping. The development of a standardised model has not only
been technically complex but also difficult at a practical level given the
existing variation in national calculation models across the continent.
The movement towards the completion and roll-out of such a model over
the next few years represents a remarkable progression on what exists at


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present. Ultimately though, the success of the method will be judged on its
rate of adoption across all Member States.
The efficiency of developing noise maps is intrinsically linked with the
development of the personal computer. When the END was first initiated,
it was a computationally intensive task to develop a noise map for an
entire city. Even in the last 10 years, the computational efficiency of
computers has increased exponentially and a city noise map can now
be developed overnight. The possibilities behind harnessing this potential
are only just being realised with the development of 3D and interactive
noise maps. For example, real sounds can be linked to maps, or maps
can be cross-referenced with noise complaints in a city, offering the general public an appreciation and understanding of the concepts associated
with environmental acoustics.
Another significant development is the introduction of common
indicators of annoyance (Lden) and sleep disturbance (Lnight) across the

EU as part of the END. While there are some concerns about the viability
of these indicators for doing what they were introduced to do, their introduction has nevertheless ensured that there is a common basis for comparison (at least in terms of indicators) across the continent. This is important
because prior to their introduction, a wide variety of indicators were used
for assessing annoyance and sleep disturbance within individual nations.
However, the use of supplemental indicators, which is catered for under
the END, needs to be encouraged. In fact, future research should focus
on the potential benefits of supplemental noise indicators which may be
used in parallel with Lden and Lnight in the strategic noise mapping process.
Acousticians now also have access to a range of noise-monitoring
equipment that was previously unimaginable. It is now possible to measure noise over very long time periods and to monitor results in real time.
It is also possible to remotely access real-time sound recordings and analyse frequency spectra at the click of a button. The key challenge for the
future is to utilise this technology in the future development of noise
and noise assessment studies and noise policy. The need for a single number noise indicator is needed so policy and guideline limits can be changed
to offer more detailed noise criteria and thus enhanced protection for citizens. Consider, for example, the A-weighting system which was
designed to reflect how the human ear responds to sounds at different frequencies. Modern sound level meters can now produce one-third octave
analyses as standard, so design goals may be set in terms of third octave
levels instead of an overall dB(A) figure.
The other main area of progress has been in relation to raising awareness. While we have no concrete data which shows that people are more
aware of the problems associated with noise pollution now than they were
in the past, anecdotal evidence as well as evidence from EU surveys of
public attitudes would seem to suggest that there is indeed a greater


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awareness of noise pollution among the general public today than in the
past. For example, a recent Eurobarometer survey showed that 44% of
Europeans believe that noise affects human health to a ‘large extent’, an

increase of 3% since 2006 (European Commission, 2010). The increase suggests, albeit tentatively, that awareness of noise-related health issues is
increasing. There is little doubt that this improved awareness is related
to the introduction of the END. The legislation mandates that the results
of the strategic noise mapping process be disseminated to the general public. While there has been some problems with this (alluded to in the next
section), it still remains that noise pollution information is now more
accessible and readily available to the general population of the EU than
at any time in the past. This is a significant achievement. Moreover, as well
as raising awareness among the general public, understanding has also
been raised among local authority officials, administrators and policymakers about noise pollution issues. The manner in which the END has
been implemented among Member States effectively ensures that local,
national and regional officials must co-operate and exchange information,
data and knowledge about the noise mapping process in order to ensure
national compliance. Moreover, there is now also a much greater degree of
dialogue among national officials and policymakers across the EU than
there has ever been before.
Perhaps one of the more slow moving areas in terms of progress in
recent years has been in the area of noise pollution mitigation. Considerable research has been undertaken, and is ongoing, assessing how mitigation approaches can be improved both in a technical sense and how they
can be made more cost effective in an increasingly strained financial environment. Improvements have been made in how buildings are insulated,
in more efficient low noise road surfaces, better track and braking systems
for railways as well as improvements for design of quieter aircraft, to point
out only a handful of progressions. Indeed, researchers have also investigated more innovative solutions to noise mitigation though the concept of
soundscapes which aims to focus more on the positive sounds associated
with a particular environment (through masking negative sound sources)
rather than emphasising the negative aspects of a place (see Chapter 7,
Section 7.5.4). However, the pace of progress in this area could certainly
be faster. In this respect, noise mitigation is one of the areas that simply
must be targeted for significantly more research over the coming years
if the problem of environmental noise pollution is to be reduced not only
at the European level but also throughout the world.
Over the last two decades, the volume of research activity in the area of

environmental noise pollution has increased quite substantially. There
have been significant improvements in our understanding particularly
of the devices used to measure noise and how noise is modelled at the
source as well as how it propagates away from the source. Commercial


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software has also improved dramatically, meaning that noise calculations
can be completed for much larger study areas than in the past. Moreover,
since the introduction of the END into legislation there has been a raft of
new research completed not only examining the extent of population
exposure in various countries around the world but also investigating
ways in which the strategic noise mapping process can be improved or
utilised to assist with understanding other noise pollution issues beyond
the remit of the END (e.g. noise insulation of buildings, 3D visualisation
of noise mapping results). Chapter 4 (Section 4.4) provides details of
some of this research, but it is far from being exhaustive. The upshot of
the increase in research output in environmental noise pollution is that
we now have a much better understanding of environmental noise issues
and how they might need to be addressed than at any point in the
recent past.

8.2 LIMITATIONS AND FUTURE
RESEARCH PRIORITIES
The foregoing section has highlighted the extent of the progress that has
been made with respect to environmental noise pollution over the last
decade. Nevertheless, this does not mean that the situation is perfect

and does not require any further investigation or scrutiny. Rather, there
are significant areas where our understanding of environmental noise
issues needs further improvement and if recent progress has taught us
anything it is precisely that our knowledge is quite limited in a number
of areas related to noise pollution, its negative effects and how to control
them. In fact, it is the role of scholars, in particular, to identify areas that
might be worthy of more scrutiny and offer suggestions for potential solutions that should be investigated through more targeted research that
serves as evidence for improving policy.
While the END is symbolic of the significant progress that has been
made in recent years, the sheer scale of its ambition as a large-scale noise
assessment and reduction programme has meant that it was always destined for teething problems after it was introduced into legislation. One of
the major weaknesses of the END and any environmental noise legislation
is the lack of clearly stated limit values, particularly for the night-time
period, above which noise levels are not legally tolerated. A recent report
commissioned by the EU has pointed out that this weakens the impact of
the END because it fails to set a common level of ambition for the EU with
regard to noise quality (Guarinoni et al., 2012). While it is understandable
that noise limits were not put in place immediately under the terms of
the END, enough time has now passed and significant intellectual and
administrative capacity been developed to ensure that the EU can now


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move towards even more ambitious noise reduction targets. These should
take the form of limit values that are introduced progressively under
amendments to the END legislation. Indeed, 19 Member States (out of
27) already have legally enforced noise limit values. If these are exceeded,

measures to control noise and/or to insulate exposed populations are
implemented. In some nations, financial penalties are also imposed on
those responsible for the source of the pollution. This has led Guarinoni
et al. (2012) to recommend that trigger values rather than legally
binding limit values should be introduced in the short term with a view
to moving towards imposing limit values in the medium term future
across the EU.
In relation to the END, there is little doubt that more concrete guidance
information needs to be provided to Member States on implementation.
In this context, there is certainly scope for guidance information to be
provided on strategic noise mapping, action planning, trigger values,
the definition of quiet areas as well as specific ways in which results
can be disseminated to the general public. In these areas, perhaps the most
pressing need for guidance is in the area of noise action planning as well as
in the definition of quiet areas. Both of these areas seem to be relatively
poorly understood (European Commission, 2011), and the expectation
of how the END is to be implemented in these areas is quite confused
at present. In relation to action plans, while several Member States produced national guidance on action planning for the first phase of END
implementation, many did not. However, the documents already produced by individual nations could certainly be used as a basis from which
to develop EU guidance for future rounds of END implementation. Turning to quiet areas, it is clear that the END leaves considerable (perhaps too
much) discretion at the hands of Member States in delimiting quiet areas.
This needs to be addressed in future research and practice because at the
moment, the preservation of areas of good sound quality appears very
much as an afterthought in END implementation. Indeed, this has been
recognised by the EU and the current EEA Expert Panel on Noise (EPoN)
is currently working to produce a green paper on the management of quiet
areas specifically within the context of END implementation (Guarinoni
et al., 2012).
The introduction of the new annoyance and sleep disturbance indicators Lden and Lnight has undoubtedly been important for standardisation
purposes across the EU. However, our knowledge of the suitability of

these indicators for adequately representing annoyance and sleep disturbance in the field remains fairly limited. To take Lnight as an example, it is
pretty rare for studies of sleep disturbance in the literature to cover the
entire 8-h night-time period. In addition, very few studies have utilised
the Lnight indicator as an expression of sleep disturbance. In fact, it is quite
likely that the Lnight noise indicator underestimates the extent of sleep


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disturbance because it averages noise over a long period effectively
smoothing out and downgrading the impact of intermittent and impulsive
noise events that are known to have a highly negative effect on sleep
patterns. Thus, our knowledge of the suitability of such indicators for
doing what they are intended to do is somewhat flimsy. If we are to continue to use these indicators in future rounds of noise mapping and
population exposure estimation at the EU level, research will need to
prioritise investigating their suitability or otherwise for achieving their
stated intentions. Bearing this in mind, future research should focus
on improving the prediction of subjective sleep disturbance by adding
the possibility within the END of utilising noise descriptors other than
Lnight. These could include descriptors penalising noise in the early or late
part of the night-time period, descriptors of peak noise levels or noise
events to assess the problem of intermittent or impulsive noise more
effectively (e.g. SEL, Lpeak, Lmax).
While the END has been highly successful at seeking and enforcing
international agreement on large-scale strategic noise pollution issues, it
has been much less successful at utilising the results of the process to drive
real change and action at the local level. In fact, the recently published
END implementation report has pointed out that despite the wide-scale

noise mapping and exposure estimation of EU populations, it is likely that
noise pollution has not been reduced at all (European Commission, 2011).
While this shortcoming is largely as a result of a lack of ambition with
regard to action planning on behalf of some nations (others have done a
very good job), it is also related to the relatively poor way in which results
of the process have been disseminated to the general public. A number of
scholars have pointed to the piecemeal way in which the public have been
invited to engage with noise pollution results and much more could be
done in this area (see Guarinoni et al., 2012; Murphy and King, 2010).
It is crucial then that in the future, this aspect (public dissemination) of
the END is given more thoughtful consideration because raising public
awareness about the extent of noise pollution issues is likely to be very
important for developing and enhancing public and indeed political support for future noise reduction measures through action planning as well
as through further legislation and policy improvements.
There are also significant limitations with how population exposure is
estimated across the EU. In large part, these limitations have been forced
either by data or by modelling limitations at the national level. In the EU,
the imminent standardisation of noise modelling techniques should eliminate the problem of modelling variations. However, the problems associated with data and the method of estimating population exposure have yet
to be dealt with satisfactorily. If these limitations are to be addressed,
serious consideration must be given to developing a standardised international database of noise input data for noise modelling and population


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exposure estimation. And there is no reason at all why this could not be
done; to a large extent, we already have a template for how this could
work with the international database on aircraft sound power characteristics (see Chapter 5). This general approach could be extended to include
other data sources necessary for noise mapping across the EU. Moreover,

the recent publication of the Common Noise Assessment Methods in the
EU (Kephalopoulos et al., 2012) document does provide the basis for
standardising how population exposure is estimated in Member States,
but refinement and additional clarifications are needed prior to its completion. Ultimately then, there is considerable scope for improvement
in understanding, controlling and ultimately reducing the problem of
environmental noise pollution, but it is likely that a key pathway towards
achieving this goal is through more research and standardisation of
approaches not only across the EU but also worldwide. Movements in this
direction would not only facilitate relative differences in exposure to be
identified across the globe but also enable more concrete indications about
the role of variations in best practice environmental noise policy to be
delimited, shared and transferred across national boundaries.
While there has been a dramatic increase in the volume of research
undertaken investigating the relationship between noise pollution exposure and its impacts on human health over the last two decades, there
remains much work to do to improve our understanding in this area.
In general terms, there is overwhelming evidence to suggest negative
health effects from environmental noise exposure. However, there are
many areas where significant association has been developed between
noise exposure and health conditions, but more research needs to be
undertaken to investigate the issue of causality more vigorously. For example, the recent WHO (2011) Burden of Disease from Environmental Noise
report clearly points out that there are some areas where there is not
yet sufficient evidence to say definitively that noise is responsible for a
particular health condition. For example, while there is increasing evidence demonstrating an association between noise exposure and
increased risk of cardiovascular disease, the existing evidence stops short
of providing any definitive statement on causality. Indeed, even in terms
of association, there are areas that are under investigated. While we know,
for example, that there is a clear association between noise exposure from
road traffic and increased risk of ischaemic heart disease, including myocardial infarction, there is less evidence for such an association with aircraft noise simply because of a lack of studies investigating the issue
(WHO, 2011). In a similar vein, there have been very few studies that have
investigated the relationship between rail noise exposure and cardiovascular disease and thus we must reserve judgement on the nature of these

relationships until more evidence is made available. Indeed, the link
between noise exposure and tinnitus, while well established, remains


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fairly poorly understood. In terms of hearing loss, the WHO (2011, p. 100)
recently concluded that ‘epidemiological studies linking hearing impairment to environmental noise exposure are so sparse that any generalisation can be considered exploratory and speculative’. Moreover, the WHO
(2011) also suggest that there is not yet sufficient evidence to suggest that
children are more vulnerable (in that they react differently) to noise
exposure than other population groups despite some studies suggesting
otherwise. In this regard, the reaction of children and other potentially
vulnerable groups (e.g. the elderly) to excessive noise exposure needs to
be investigated more definitively. On the other hand, existing evidence does
suggest that there is a causal relationship between noise exposure and sleep
disturbance and ‘depending on noise levels, may impair behaviour and
well-being during the subsequent period awake’ (WHO, 2011, p. 55). There
is also sufficient evidence, indicating a causal relationship between noise
exposure and annoyance. Clearly then, while our present understanding
of these relationships is much greater than at any time in the past, there
are some relationships that will require much more significant scrutiny if
we are to establish more definitive statements on the impacts or otherwise
of environmental noise pollution on public health outcomes.
Finally, the role that technology can and will play in the future prevalence of noise pollution is likely to be considerable. Over the last half
decade, the major improvements that have been seen in noise reduction
emissions from transport vehicles, in particular cars and aeroplanes, have
come primarily from improvements in engine and tyre technology. Looking to the future, there is little doubt that technology will remain pivotal to
creating quieter urban and rural environments. One area where this is

likely to be crucial in the not too distant future is in relation to the imminent development of electric cars. Given that road traffic noise is the most
important source of environmental noise, there is a significant opportunity to reduce pollution and associated health problems through the wider
substitution and use of these vehicles over chemically powered ones. Electric cars are much quieter than chemically powered ones although at the
moment battery technology does not quite appear to be at a stage that
would ensure their widespread adoption. Nevertheless, although they
are likely to be equipped with sound that will act as a substitute for engine
noise, if it is directional, short range and generally pleasing (or at least not
annoying), these vehicles have the potential to allow for a significant
reduction in annoyance and sleep disturbance.
Technology will also be important in other areas. The development of
low-cost noise measurement devices is likely to play a greater role in the
future. The development of noise apps for Smartphones, while currently
not very reliable, is likely to become more important as technology
improves in the future. It is likely then that the public could contribute
much more significantly than at present in providing noise measurement


260

8. CONCLUSIONS AND FUTURE DIRECTIONS

data through mobile/cell phones in a form of ‘citizen science’ (D’Hondt
et al., 2013). The technology utilised in mobile/cell phones is MicroElectroMechanical Systems (MEMS) microphones which can be constructed
relatively cheaply and at a low cost. As the reliability of these microphones
is improved in the future, they will undoubtedly provide a much better
scope for measurement-based noise mapping or indeed low-cost validation of noise modelling results. We can only hope that these, together with
other improvements, will provide for a much quieter future and that quite
soon we can truly refer to environmental noise as the forgotten pollutant.

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